1. Field of the Invention
The present invention is directed to methods of wastewater treatment and the by-products thereof, useful in a plurality of settings, such as, for example, municipal and industrial applications. More specifically, the invention relates to methods for treating leachate to produce useful by-products, such as sodium hypochlorite.
2. Description of the Background
Disposal of wastewater is a major problem facing industries and communities. There are numerous sources of wastewater, such as, for example, industrial pollution, industrial lagoons, human waste and landfills.
Landfills contain a wide variety of wastes which undergo decomposition. When rainfall penetrates landfill sites, the rainwater is mixed with the decomposing waste and produces wastewater known as leachate, which is laden with hazardous chemicals. Landfills are required to have landfill liners to prevent against leakage, as well as leachate collection and removal systems and leak detection systems. The liners are generally manufactured from plastic materials, clay substances or ash. Rainfall within these lined landfills or cells generates leachate which must be collected, treated, and disposed of to the satisfaction of environmental regulations.
Landfills generally have an on site leachate management facility (LMF) designed to manage, process and provide adequate capacity to treat the leachate. However, excessive rainfall amounts and/or operational problems can result in excess leachate being stored at the LMF facilities. Off site disposal of the leachate can assist in reducing the volume of on site leachate, but also generates additional problems because of the hazards and costs associated with transporting the toxic wastewater. Considering the volume of leachate generated at landfills and the excess leachate being stored on site, cost-efficient and safe alternate treatment and disposal methods are needed.
The present invention overcomes the problems and disadvantages associated with current strategies and designs and provides cost-effective and safe methods and systems for processing leachate and wastewater to produce useful products.
Accordingly, one embodiment of the invention is directed to a method for processing wastewater comprising the steps of exposing the wastewater to a first magnetic treatment and exposing the magnetized wastewater to an electrolytic treatment to produce at least one useful product, such as sodium hypochlorite. Preferably, the step of exposing the wastewater to the first magnetic treatment comprises passing the wastewater through a passageway or spool, the passageway having a plurality of magnets disposed circumferentially around the passageway. Exposing the wastewater to electrolytic treatment preferably comprises passing the wastewater through an electrolytic cell
In a preferred embodiment, the method further comprises filtering the wastewater prior to exposing to the first magnetic treatment. Filtering may comprise passing the wastewater through a filter or a screening device or both. The filter may comprise a sand media base with an underdrain assembly. The screening device may comprise a static or rotating fine mesh screen.
The method may optionally further comprise exposing the magnetized wastewater to a second magnetic treatment. The method may optionally further comprise aerating the filtered wastewater. Aeration may be accomplished by passing the filtered wastewater through an air stripping tower. Preferably, the air stripping tower comprises: a mist distributor for distributing the wastewater; a packed bed disposed below the mist distributor, which contains packing material so that wastewater from the mist distributor flows downward over the packing material; and aerating means disposed below the packed bed for forcing air upwards over the packing material. Alternately, aerating may comprise passing the filtered wastewater through an aeration system, the aeration system comprising a tank for holding the wastewater and means disposed at the bottom of the tank for diffusing air upwards through the wastewater.
Optionally, the method may further comprise recycling the wastewater, by exposing the wastewater to a third magnetic treatment and a second electrolytic treatment. Alternately, recycling may further comprise subjecting the wastewater to a second aerating step before exposing the wastewater to the third magnetic treatment. If desired, the method may include a step of conditioning the wastewater by adding metal ions or salts to the wastewater.
Another embodiment of the invention is directed to a system for processing wastewater comprising a first magnetic treatment zone and an electrolytic treatment zone fluidly coupled to and disposed downstream from the magnetic treatment zone. The first magnetic treatment zone preferably comprises a cylindrical passageway or spool having a plurality of magnets disposed circumferentially around the passageway. Preferably, the system further comprises a filtration zone fluidly coupled to and disposed upstream from the first magnetic treatment zone. The filtration zone may comprise a filter or screening device or both, such as those described above.
Preferably, the system further comprises a second magnetic treatment zone similar to the first fluidly coupled to and disposed downstream from the first magnetic treatment zone, and an aerating zone fluidly coupled to and disposed downstream from the filtration zone. The aerating zone may comprise an air stripping tower or an aeration system, such as those described above.
Optionally, the system may comprise means for recycling the wastewater to the second magnetic treatment zone or, alternately, further upstream to the aeration zone. If desired, the system may comprise means for bypassing one or more of the various zones, such as means for bypassing the filtration zone, the aerating zone, the first magnetic zone, the second magnetic zone or the electrolytic treatment zone.
Another embodiment is directed to an apparatus for removing a volatile hazardous substance, such as H2S, from wastewater comprising: a mist distributor for distributing wastewater; a packed bed disposed below the mist distributor, the bed containing packing material, and wherein wastewater from the mist distributor flows downward over the packing material; and aerating means disposed below the packed bed for forcing air upwards over the packing material.
Another embodiment is directed to a method for removing volatile hazardous substances, such as H2S, from wastewater comprising: distributing wastewater over a packed bed using a mist distributor, the packed bed disposed below the mist distributor and containing packing material; allowing the wastewater from the mist distributor to flow downward over the packing material; and aerating the wastewater by providing aerating means disposed below the packed bed to force air upwards over the packing material.
Other embodiments and advantages of the invention are set forth in part in the description which follows, and in part, will be obvious from this description, or may be learned from the practice of the invention.